Recommendation for an oral mucosal contouring method in nasopharyngeal carcinoma patients receiving tomotherapy

Objective To evaluate the value of two oral mucosal contouring methods for predicting acute radiation-induced oral mucositis (A-ROM) in nasopharyngeal carcinoma (NPC) patients. Methods A total of 150 AJCC 7th stage Ⅱ-IVB NPCs receiving radical tomotherapy (TOMO) in Zhejiang Cancer Hospital from 2017 to 2019 were included in this prospective observational study. Oral cavity contour (OCC) and mucosal surface contour (MSC) were applied to delineate the oral mucosal structure. A-ROM grade was prospectively assessed and recorded weekly according to RTOG scoring criteria. The prediction value of two methods for A-ROM was statistically compared. Results The incidence rate of ≥3 grade A-ROM was 33.3%. In univariate analysis, V5, V10, V15, V45, V50, V55, V60, V65 and V70 of OCC and V5, V10, V50, V55, V60, V65, V70 and Dmean of MSC were significantly correlated with the risk of ≥3 grade A-ROM (all P<0.05). In binary logistic regression analysis, gender and smoking were significantly associated with the incidence of ≥3 grade A-ROM by using OCC (male vs. female: OR=0.141, 95%CI=0.037-0.538, P=0.004; smoking vs.non-smoking: OR=5.109, 95%CI=1.413-18.470, P=0.013). For MSC, gender, smoking, N stage and MSC- V55 were the independent predictors (male vs. female: OR=0.129, 95%CI=0.032-0.519, P=0.004; smoking vs.non-smoking: OR=4.448, 95%CI=1.224-16.164, P=0.023; N stage: OR=2.291, 95%CI=1.268-4.137, P=0.006; MSC-V55: OR=1.432, 95%CI=1.008-2.033, P=0.045). The cutoff value of MSC-V55 was 7.70%, the area under ROC curve was 0.754, the sensitivity and specificity were 0.680 and 0.740, retrospectively (all P<0.001). Conclusions Compared with OCC, MSC yields a higher prediction accuracy for the severity of A-ROM in nasopharyngeal carcinoma patients receiving TOMO treatment. Key words: Nasopharyngeal neoplasms/tomography therapy; Acute radiation-induced oral mucositis; Dosimetric parameter